Abstract: The effective recovery of neptunium (Np) from spent fuel, particularly in its prevalent and poorly extractable pentavalent state, remains a significant challenge for advanced fuel cycle sustainability. Conventional solvent extraction processes require the separate introduction of chemical reductants to convert Np(Ⅴ) to the more extractable tetravalent state Np(Ⅳ), adding complexity and potential secondary waste. To address this challenge, a novel class of hydrophobic, redox-active deep eutectic solvents (DESs) was designed in this study, integrating reduction and extraction functions into a single, task-specific phase, thereby eliminating the need for external reagents. Three functionalized DESs were synthesized by combining the neutral diglycolamide extractant N,N,N',N'-tetraoctyl-3-oxapentanediamide (TODGA) as the hydrogen bond acceptor (HBA) with dihydroxybenzene isomers, catechol (CC), resorcinol (RC), or hydroquinone (HQ), as hydrogen bond donors (HBDs). The formation of TODGA-CC, TODGA-RC, and TODGA-HQ DESs was confirmed via ¹H NMR and FT-IR, revealing extensive hydrogen-bonding networks between the carbonyl groups of TODGA and the phenolic hydroxyls. These DESs exhibit favorable hydrophobicity and fluidity for liquid-liquid extraction. The extraction performance was systematically evaluated using ²³⁷Np tracer from nitric acid media. All three DESs achieve rapid extraction equilibrium within 10 minutes, with single-contact efficiencies of 81.8%, 74.5%, and 67.7% for TODGA-CC, TODGA-RC, and TODGA-HQ DESs, respectively, from 1.0 mol/L HNO₃. The performance hierarchy (CC>RC>HQ) correlates directly with the inherent reducing power of the HBD isomers. The DESs demonstrate remarkable robustness under conditions relevant to fuel reprocessing: Extraction efficiency remains high at elevated acidity (up to 2.0 mol/L HNO₃), high salinity (5.0 mol/L NaNO₃), across a temperature range of 293-313 K, and following gamma irradiation doses up to 50 kGy. Process feasibility was underscored by a five-stage cross-flow extraction, which achieves a total Np recovery exceeding 99.6%. Mechanistic investigations employing UV-vis-NIR absorption spectroscopy provide direct evidence for the in-situ reduction of Np(Ⅴ) to Np(Ⅳ) during extraction, with reduction extents matching the extraction efficiencies. NMR and FT-IR analysis using Th(Ⅳ) as a non-radioactive structural analog confirm that TODGA retains its metal-coordinating ability within the DES matrix, with carbonyl and ether oxygen atoms acting as key donor sites. Dynamic light scattering (DLS) reveals the formation of reversed micellar aggregates (30-120 nm) in the loaded organic phase, suggesting a synergistic extraction mechanism involving both direct coordination and supramolecular encapsulation. A concerted “coordination-activated reduction” mechanism is proposed to explain the high efficiency: (1) TODGA molecules pre-concentrate and weakly coordinate with Np(Ⅴ) at the liquid-liquid interface; (2) This coordination electronically activates the Np(Ⅴ) center, lowering its reduction potential; (3) The dihydroxybenzene HBDs, acting as interfacial electron donors, rapidly reduce the activated Np(Ⅴ) to Np(Ⅳ); (4) The resulting Np(Ⅳ) ion is strongly complexed by TODGA to form a hydrophobic Np(Ⅳ)-TODGA-nitrate species, which partitions into the DES phase. In conclusion, this work successfully develops a new family of multifunctional DESs that enable the efficient, in-situ reduction and extraction of Np(Ⅴ) without auxiliary reagents. The systems combine fast kinetics, high efficiency, and exceptional stability under harsh conditions. The elucidated design principle, based on integrating a metal-coordinating HBA with a redox-active HBD within a DES framework, offers a novel and green strategy for Np recovery and presents a generalizable approach for designing task-specific solvents for separating other redox-sensitive metals in hydrometallurgy and nuclear waste management.